Selective copper solvent for diolifin extraction



v in hydrocarbon fractions.

. cracked hydrocarbon fractions.

Patented Dec. 21, 1948 SELECTIVE COPPER SOLVENT FOR DIOLIFIN EXTRACTION Leland K. Beach, Mountainside, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application May 13, 1946, Serial No. 669,453

8 Claims.

This invention relates to improvements in the separation of diolefins from mixtures of saturated and unsaturated hydrocarbons and relates particularly to improvements in the separation of diolefins from hydrocarbons having two or more carbon atoms to the molecule by the use of copper solvents.

The aifinity of certain unsaturated hydrocarbonsis well known. Thermally decomposable complexes are formed between the simple olefins and diolefins and cuprous compounds such as cuprous chloride, CuCLNI-hCl complexes, etc. However, most of these cuprous compounds and complexes possess certain features such as instability and corrosiveness to metal equipment which render them unsuited for use in the commercial recovery and separation of olefins and diolefins The use of hydroxy amine complexes of copper, using cuprous chloride or formate, for the separation of olefins from mixtures of hydrocarbons is suggested in U. S. Patent 2,005,500 issued June 18, 1935, to Walter Philip Joshua and Herbert Muggletonstanley. However, the hydroxy amine copper solutions are unstable on heating to temperatures of the order of 80 C., which are required for satisfactory desorption of the hydrocarbons from the solutions.

In U, S. application Serial No. 371,998 filed December 2'7, 1940 and now Patent No. 2,370,809, for C, E. Morrell and M. W. Swaney is disclosed the 'efllcacy of the ammonlacal cuprous acetate solutions of high cuprous content for the extraction and separation of butadiene from These solutions possess high solvency for butadiene, high selectivity for butadiene over the butylenes, and high thermal stability in glass or in steel equipment.

However, these ammoniacal cuprous acetate solutions possess considerably lower solvency for the higher diolefins such as isoprene, piperylene, etc.

In U. S. application Serlal'No. 638,518 died December 29, 1945, for C. E; Morrell and M. W Swaney, the ammonia in the ammoniacal cuprous acetate complexes is replaced by monomethylamine, in partor wholly. The effectiveness of the resulting complex is improved for the extraction and concentration of the higher diolefins such as isoprene from hydrocarbon mixtures. In addition, the basic monomethylamine cuprous acetate solutions retain remarkable thermal stacuprous compounds for zoo-681.5)

bllity and are non-corrosive to metal equipment, for example, steel. However the capacity of these basic monomethylamine cuprous acetate solutions is limited.

According to the present invention, it was found that by adjusting the ratio of amine to acetate to water of a cuprous solution, the absorption capaclty of the monomethylamine cuprous acetate solution can be greatly increased as illustrated by the following table.

According to U S. Appli- According to cation Ser. No. Applicants Wt., per Wt., per

cent MIL cent L Monomethylamine--. 48 16 41 14 Acetate 18 3 34 6 Water 26 l5 l2 7 Copper ous 6 1.0 12 2 ie -e 2 0. 24 1 0.1 Purity of isoprene absorbed at 0 C. by solution in equflibrlum with isoprene of 25% purity in pentene-l 63 51 Volume 01 gaseous isoprene ol above purity absorbed per volume oicoppers0lution 4.5 17.7

It is not possible by changing the concentration of any one of the components of the solution disclosed in the U. S. application Serial No. 638,518 to arrive at a solution within the optimum range. For example, by cutting down on the amine content at the expense of the other components, both the selectivity and capacity would be found to drop considerably; by raising the acetate content, the same phenomenon would occur; by cutting down on the water, a slight increase in capacity and a'slight decrease in selectivity would result but this would be due primarily to an increase in the solubility of copper. The cuprous content of the above solutions is a maxi mum in each case and cannot be increased independentiy.

It is only by completely changing the U. S. application Serial No. 638,518 solution composition that a solution of optimum composition is found which has three to four hundred percent greater capacity.

The following table hows that the selectivity and capacity-of these optimum solutions may be I v 3 modified within limits by small changes in solution composition;

Isoprene absorption capacity and selectivity and other properties of monomethylamine cuprous acetate solutions at C'.

Absorption-Desorption Data Composition (3 s 1 11 it Fill 1 upper e co v y, c ency, $g Mllvlatrez Molarity lisurtity 11/1 ggggggg M0173??- o a y x rac prone 0 es Ratio Raflflnate CUQH' z 5 13. 2 0. 42 a 5 2. 0 0. 12 2 5 1. 9 0. 12 o 2. 5 0.12 0 14. a 0. s9 0 9.9 0.41 t. 0 0.28 3.0 2.1 7 0.14 0 4. 2 0.16 30 11.0 i 0.61 3 0 6.0 0. 28 3 0 12.0 0. 65 34 22.0 1.00 3,0 2.6 0.18 3 0 1. 9 0. l8

1 In presence of pentene-l. Trimethylethylene used in othe 1 experiments.

In general, the amine to acetate mol ratio that may be used varies from 1.5 to 7; 2.0 to 3.5 being preferred. The water content thatmay be used varies from 1 to mols per liter; 1.5 to 10 mols per liter being preferred. The cuprous content is between about 1.0 to 2.5 mols per liter, preferably above 1.5 mols per liter. The presence of some cuprlc copper is desirable to the solution stability and a pH above about 10 is also desirable in order to reduce. corrosion to steel. The preferred range of compositions are expressed in the accompanying table in terms of wt and normalities.

Weight, per cent MIL Monomethylamine 37-45 12 -16 Acetate 25-40 4 7 Water 1-25 1 -15 10-13 1. 7- 2. 3 ie 0-2 0 0.4

A comparison of methylamine cuprous solution capacity for diolefins with that of ammoniacal cuprous solutions is shown in the following tables.

dine, aniline, quinoline, piperidine, urea, acetonitrile, were tried as well as the anions, sulfate, formate,'propionate, tartrate, lactate and chloride, but from the standpoint of corrosion, chemical and thermal stability, vapor pressure, cost, capacity, selectivity, freezing point etc., the monomethylamine cuprous acetate solutions were found to be most efllcient.

A solution containing a monomethylamine/acetate mole ratio of 2.0/1.0, 5 M/L water and 1.8 M/L copper, was heated 17 days at C. in pres ence of polished steel strips. No corrosion, plating or. precipitation occurred. A similar solution containing 2.5/1.0 amine to acetate ratio, 5.0 M/L water and 2.1 M/L copper caused no corrosion or plating out at C. after two days.

This solution may be used to separate the isomers of piperylene, that is, cis-piperylene from trans-piperylene and also inthe separation and concentration of hexadiene.

vWhat is claimed is: I

1. Improvement in separating an unsaturated hydrocarbon from a mixture containing a relatively more saturated hydrocarbon which comprises absorbing the said unsaturated hydrocar- Extraction at 0 C-Gaseous Butadiene in Extraction at 0 0.Liquld Isoprene in 'lrimethylcthylone Per cent Isoprene involume Gaseous Cs Delsorbedf er v0 ume o fi gggg fifgfi opper Solution Ammoniacnl Cuprous Acetate 35 83 1. a Monomethylamine I Cuprous Acetate- 35 83 13, 9

l 2.0/1, amine/acetate mol ratio, 5 MIL Water, 1.8 MIL total copper.

bon in a solution of an alkyl amine cuprous acetate complex containing from 1.5 to 10 mols of water per liter and in which the alkyl amine has from 1-4 carbon atoms and the mol ratio of alkyl amine to anion varies from 2.0 to 3.5.

2. Improvement in separating an unsaturated hydrocarbon from a mixture containing also a relatively more saturated hydrocarbon which comprises absorbing the said unsaturated hydrocarbon in a solution of a primary alkyl amine cuprous acetate complex containing from 1.5 to

10 mols of water and in which the alkyl amine has from 1-4 carbon atoms and the mol ratio of alkyl amine to total anion varies from 2.0 to 3.5.

3. Improvement in separating a diolefin from a mixture containing a relatively more saturated hydrocarbon which comprises absorbing the diolefln in an aqueous solution of a methylamine cuprous acetate complex containing from 1.5 to 10 mols of water per liter and in which the amine to total anion mol ratio varies from 2.0 to 3.5 and separating said solution and desorbing the diolefin.

4. Improvement in separating isoprene from a mixture with a more saturated hydrocarbon which comprises absorbing the isoprene in an aqueous solution of a monomethylamine cuprous acetate complex containing from 1.5 to 10 mols of water per liter and in which the amine to total anion mol ratio varies from 2.0 to 3.5, separating the cuprous acetate solution and desorbing the isoprene.

5. Improvement in separating isoprene from a mixture with pentenes which comprises absorbing the isoprene in an aqueous solution of a monomethylamlne cuprous acetate complex containing from 1.5 to 10 mols of water per liter and in which the amine to total acetate mol ratio varies from 2.0 to 3.5, separating the cuprous solution and desorbing the isoprene.

6. Improvement in separating piperylene from a mixture with a more saturated hydrocarbon which comprises absorbing the piperylene in an aqueous solution of a mono-methylamine cuprous acetate complex containin from 1.5 to 10 mols of water per liter and in which the amine to total anion mol ratio varies from 2.0 to 3.5, separating the cuprous acetate solution and desorblng pentadiene.

7. Improvement in separting methyl pentadienes from a mixture with a more saturated hydrocarbon which comprises absorbing the methyl pentadienes in an aqueous solution of a monomethylamine cuprous acetate complex containing from 1.5 to 10 mols of water per liter and in which the amine to total anion mol ratio varies from 2.0 to 3.5, separating the cuprous acetate solution and desorbing the methyl pentadienes.

8. Improvement in separating a diolefln from a mixture containing also a relatively more saturated hydrocarbon which comprises absorbing the said unsaturated hydrocarbon in a solution of an alkyl amine cuprous acetate complex containing from 1.5 to 10 mols of water per liter in which the amine to total anion mol ratio varies from 2.0 to 3.5 and the alkyl amine has from 1 to 4 carbon atoms inclusive.

LELAND K. BEACH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATEN'IS 

